Following Doing things to the whole map canvas in QGIS and adding some blending to the mix (he-he), I ended up with this map. Nothing you could not do with simple post-processing in a raster image editor or even QGIS’ map composer I guess.

It was simply the result of playing around, there probably is a faster or more efficient way.

First give your geometries some fancy texture with Raster image fill (left). Then constrict its display to just some blurry borders by using a grey fill, Blur draw effect with maximum strength and the Dodge Layer blending mode (right).

You could probably skip the texture for the geometry but I did not manage to get a similarly nice effect with a Simple fill.

Use the trick from Doing things to the whole map canvas in QGIS to fill your canvas with a polygon and give that a nice texture as well. Use Multiply as Layer blending mode and get social media hype for that unbelievable stain can you believe it looks like that???

From the same session comes this beauty (mostly due to Tom Patterson’s shading of course ;) ):

Due to a minor bug in QGIS you need a very recent testing build. 2.16.3 is not recent enough but 2.16.4 would be.

For cool tricks like vignetting or other eye candy, having a geometry that spans the whole map canvas in QGIS can be very useful.

Using the @map_* Variables available in expressions in combination with a Geometry generator style allows you to do this.

@map_extent_center returns a Point geometry of the current map canvas center, with x(@map_extent_center) and y(@map_extent_center) you get the x and y coordinates of it in the current CRS.
@map_extent_width and @map_extent_height return the width respectively height of the map canvas in CRS units.

Our goal is to create a polygon that exactly matches the map canvas extents. Some simple math gets you there.

First create Points for each of the corners by alternating the x+/-width and y+/-height. Then create a Line from all of them (the last point does not need to be the first again, make_polygon does that for you). And use the line as outer ring for a Polygon.

make_polygon(
 make_line(
  make_point(x(@map_extent_center)-@map_extent_width/2, y(@map_extent_center)-@map_extent_height/2),
  make_point(x(@map_extent_center)+@map_extent_width/2, y(@map_extent_center)-@map_extent_height/2),
  make_point(x(@map_extent_center)+@map_extent_width/2, y(@map_extent_center)+@map_extent_height/2),
  make_point(x(@map_extent_center)-@map_extent_width/2, y(@map_extent_center)+@map_extent_height/2)
 )
)

To actually see this, you need to use the style on a layer with at least one feature that is always visible where you want to focus your map canvas. Just make a polygon layer with one polygon that encloses the whole area. The layer must be in the same CRS as the project I think.

You now have a Polygon that corresponds with the map canvas. Give it a radial gradient fill with some transparency and party!

All aerial images in the examples are

Lizenz: Datenlizenz Deutschland Namensnennung 2.0
Namensnennung: Freie und Hansestadt Hamburg, Landesbetrieb Geoinformation und Vermessung
http://daten-hamburg.de/geographie_geologie_geobasisdaten/digitale_orthophotos/DOP20/DOP20_HH_fruehjahrsbefliegung_2015.zip

To make sure the feature you want to highlight is in the center, you could use another layer and @map_extent_center.

Yes, this totally is a hack but it’s fun!

Daniel P. Huffman shared this gorgeous map earlier. ArcMap just got the functionality to create such contour lines.

Naturally I had to try to re-create that style in QGIS. I semi-succeeded:

You have a DEM, eg mtsthelens_after.zip. Generate a hillshade from DEM. Generate contour lines from DEM.

Split the lines by segment, for example with the “Network” plugin. Select all features on your layer and then use its “Split” function.
Calculate the azimuth of each line. See this magical formula (I wish QGIS would have a function ready).
Rotate the angle according to your hillshade light angle. For example:
CASE
 WHEN ("azimuth"+270) > 360
  THEN ("azimuth"+270-360)/500
 ELSE ("azimuth"+270)/500
END
And use that to scale your lines’ widths (the 500 is a constant factor here to get them small enough).

Disable all layers but hillshade and contour lines.
Move hillshade above contour lines.
Set map background to black (equals 0 in the blending multiplication later).
Use black to white as color ramp for the hillshade.
Set hillshade’s blending mode to multiply.
You now have the bright parts of the contour lines. Unfortunately QGIS does not yet support blending modes for whole groups so you will have to combine this with the next step in a raster graphics tool of your choice. Gimp works fine.
Take a screenshot of something.

Invert hillshade color ramp to white to black.
Rotate your angle by 180 (so it would be 90 instead of 270 in the example above).
You now have the dark lines.
Take another screenshot.

Add both images to a image in Gimp, Color to Alpha with black, invert the dark one, choose nice background, done!

This is still pretty rough as it’s mostly hack after hack and not “done properly”™. The blending adds some shadows where there should not be. In a way the lines end up being same width because of this. The scaling was done arbitrarily, there is probably some smart way with a better scale. Some fancy smoothing of the lines would look great. Coloring the areas between the lines would probably improve it as well. Once QGIS gets support for blending modes of groups, this will be much easier.